There is a widely known image processor for constructing a virtual three-dimensional space in a memory means of a computer, then disposing an object in the virtual three-dimensional space, and visualizing the picture of the space. With the device, the states of the objects, including the position, posture, and so forth thereof, disposed in the virtual three-dimensional space are updated at a predetermined time interval (for example, 1/60 or 1/30 second), so that an image showing the virtual three-dimensional space can be changed on a real time basis. In the above, however, it is difficult to update the states of many objects in a limited period of time, or 1/60 second. This difficulty is addressed by the device disclosed in the Japanese Patent Laid-open Publication No. Hei 10-307905 (see FIGS. 2 and 3), by sequentially excluding a predetermined unnoticeable object from images to be displayed.